A mobile phone (also known as a cellular phone, and a cell phone) enables its user to make and receive telephone calls over a cellular communication network while moving around a wide geographic area. To allow hands-free operation of a mobile phone, a headset is often used alongside the mobile phone during a phone call. A headset has a pair of left and right earphones or headphones combined with a microphone, or one headphone with a microphone, in a way that can be worn by the user in a hands-free manner (e.g., as an over-the-head unit, a tethered and wired unit, a wireless ear worn unit). Headsets provide the equivalent functionality of a telephone handset but with hands-free operation.
FIG. 1 illustrates a detailed diagram of a cellular phone 130 that works together with a Bluetooth headset 110 to enable hands-free operation during a telephone call. Specifically, this figure shows a Bluetooth headset 110 connected to a cellular phone 130 through a Bluetooth link 160. The Bluetooth headset 110 includes a Bluetooth audio decoder 112, a Bluetooth audio encoder 115, a Bluetooth flow/rate control logic 118, a Bluetooth modem and radio module 120, a speaker 122, and a microphone 125. The cellular phone 130 enables a near-end user to make and receive telephone calls to or from a far-end user over a VoLTE link 165. The cellular phone 130 includes a Bluetooth modem and radio module 132, a Bluetooth audio encoder 135, a Bluetooth audio decoder 138, an audio processing unit 140, a Bluetooth flow/rate control logic 142, an Adaptive Multi-Rate (AMR) audio decoder 145, an AMR audio encoder 148, a cellular flow/rate control logic 152, and a baseband radio and modem 150.
During a telephone call, the baseband radio and modem 150 of the cellular phone 130 receives downlink cellular packets from the far-end user through the VoLTE link 165. The downlink cellular packets contain a downlink audio signal that is encoded with a speech coding standard such as adaptive multi-rate wideband (AMR-WB) for transmission over the VoLTE link 165. The baseband radio and modem 150 sends the cellular packets to the AMR audio decoder 145. The AMR audio decoder 145 decodes the cellular packets into an audio stream and sends the stream to the audio processing unit 140. The audio processing unit 140 processes the stream to enhance audio quality and sends the processed stream to the Bluetooth audio encoder 135. The Bluetooth audio encoder 135 encodes the processed stream into Bluetooth packets based on an audio subband codec such as high-efficiency advanced audio coding (HE-AAC) or low complexity subband coding (SBC). The Bluetooth audio encoder 135 sends the Bluetooth packets to the Bluetooth modem and radio module 132, which then transmits the Bluetooth packets to via the Bluetooth link 160. The Bluetooth flow/rate control logic 142 manages the rate of data transmission from the mobile device 130 to the Bluetooth headset 110 by controlling the encoding of Bluetooth packets at the Bluetooth audio encoder 135.
The Bluetooth modem and radio module 120 of the Bluetooth headset 110 receives the Bluetooth packets from the cellular phone 130 through the Bluetooth link 160. The Bluetooth modem and radio module 120 then sends the Bluetooth packets to the Bluetooth audio decoder 112, which decodes the Bluetooth packets into an audio signal stream. The speaker 122 receives the audio signal stream and converts it into sound for the user of the Bluetooth headset 110.
The microphone 125 of the Bluetooth headset 110 produces an uplink audio signal stream. The Bluetooth audio encoder 115 encodes the uplink audio signal into Bluetooth packets. The Bluetooth flow/rate control logic 118 manages the rate of data transmission from the Bluetooth headset 110 to the cellular phone 130 by controlling the encoding of Bluetooth packets at the Bluetooth audio encoder 115. The Bluetooth modem and radio module 120 receives the Bluetooth packets from the Bluetooth audio encoder 115 and transmits them via the Bluetooth link 160.
The local modem and radio module 132 of the cellular phone 130 receives the Bluetooth packets from the Bluetooth headset 110 through the Bluetooth link 160. The local modem and radio module 132 then sends the Bluetooth packets to the Bluetooth audio decoder 138, which decodes the Bluetooth packets into an audio signal stream. The audio processing unit 140 may process the audio signal stream to enhance audio quality and send the processed audio signal stream to the AMR audio encoder 148. The AMR audio encoder 148 encodes the processed audio signal stream into uplink cellular packets and sends the uplink cellular packets to the baseband radio and modem 150. The uplink cellular packets contain the uplink audio signal that is encoded with a speech coding standard such as adaptive multi-rate wideband (AMR-WB) for transmission over the VoLTE link 165. The cellular flow/rate control logic 152 manages the rate of data transmission from the cellular phone 130 to the VoLTE link 165 by controlling the encoding of cellular packets at the AMR audio encoder 148. The baseband radio and modem 150 sends the uplink cellular packets to the device of the far-end user through the VoLTE link 165.
As illustrated in FIG. 1, during a telephone call, the incoming or downlink audio packets are decoded by the AMR audio decoder 145 and then encoded by the Bluetooth audio encoder 135 at the cellular phone 130, and then decoded by the Bluetooth audio decoder 112 at the Bluetooth headset 110. During the same telephone call, the outgoing or uplink audio packets are encoded by the Bluetooth audio encoder 115 at the Bluetooth headset 110, and then decoded by the Bluetooth audio decoder 138 and encoded by the AMR audio encoder 148 at the cellular phone 130. The flow control and buffering is done at multiple places, e.g., by the Bluetooth flow/rate control logic 118 at the Bluetooth headset 110, and the Bluetooth flow/rate control logic 142 and cellular flow/rate control logic 152 at the cellular phone 130.